A precise definition of a workload is elusive, but a commonly accepted definition is the hypothetical relationship between a group or individual human operator and task demands.

The assessment of operator workload has a vital impact on the design of new human-machine systems. By evaluating operator workload during the design of a new system, or iteration of an existing system, problems such as workload [bottlenecks and overload can be identified. As the human operator is a central part of a human-machine system, the correction of these problems is necessary for the operation of safe and efficient systems.